Automatic telephone exchanges



Aug l1, 1959 A. A. cHuBB ErAL Re. 24,680

AUTOMATIC TELEPHONE EXCHANGES original Filed sept. 1s, 1951 2Sheets-Sheet l ATTORNEY I 2 Sheets-Sheet 2 original Filed sept. 1s, 1951ni ammi Q Nui m NUES cmo:

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/NvENTo/s FET "Huss fwn@ Vgn/:avm MUR/re Mols@ L A Tron/ver UnitedStates Patent l 'i Ottawa, Ontario, Canada, assignors to The GeneralElectric Company Limited, London, England @riginal No. 2,732,433, `datedJanuary v24, V1956, Serial No. 247,073, September 18, 1951. ,Application:for `reissue October 29, 179358, Serial No. 770,889

'Claims priority, application Great Britain lSeptember 22, 1950 -4Claims. (Cl. 179-18) Matter enclosed in heavy brackets I] appears intheoriginal Apatent but forms `no vpart o'f lthis reissue specification;matter rprinted in `italics indicates the additions made by reissue.

The present inventionrelates to coding devices suitable for use in anautomatic exchange asdescribed inthe speccation of said cto-pending U.S.patent application, Serial No. 2471 ,'072.

In the automatic exchange vdescribed .in the aforesaid co-'pendingpatentapplication a plurality .of communication channels are provided, and inresponse toa calling signal from a calling subscriber a -ree one ofthese channels is selected. "In response to dialling signals the calledsubscriber is called and the identicationof the lselected free channel`is transmitted to the called subscribers terminal equipment. 'In orderto vachieve this a routing deviceis used and maybe as described in thespecication of co-pending U.S. patent .application Serial No. 247,233,tiled September 19, 1951. This routing device requires a set of two ormore control signals of predetermined characteristic to be applied toVits (input terminal in order to establish a connection with one ofitsoutput terminals.

An object oct the present invention is to provide a coding ,devicesuitable for storing dialling signals from `a calling subscriber,converting these signals into a set of 'control signals suitable forapplication to the aforesaid routing device,'and in addition giving thecontrol signals a characteristic ,identified with the aforesaid selectedfree channel.

According tothe present invention a -coding device comprises two or moreselector switching devices, each having a plurality o'f input terminals,an output terminal, and 4being adapted, Tin response to ydiierentdialling signals to connect 'different ones of the inputterminals to theoutput terminal, means 4for applying control voltages of 'differ-ent,predetermined characteristics tothe input terminalsrespectively ofthelselector switching devices, means for combining the control voltagesappearing attheoutput terminals of Ithe several selector 'switchingdevices to 'form a set,andmeans for Vadding a further characteristic to-the vset of control voltages. Where-the yseveral channels vin theautomatic exchange ldescribed in the first named coepending applicationare constituted 'by interlaced lpulsetrains, the means for adding thefurther characteristic :to the lcombined control Vvoltages may'comprisea gate device vto which the 'combined control voltages are applied.Pulses in the selected free channel maybe `applied to the gate device toopen the gate recurrently whereby the combined control voltages appearat the 'output ofthe gate only during'each pulse in the selectedchannel. "-Ihe means for adding the further `characteristic may comprisemeans for combining 4further voltages with -the set, lthe ffurther`voltages having characteristics `ind'ependentof fthosein the set. Forexample the ffurther :voltages :may Pbe representative :of itheaforesaid selected ifree channel.

y, Re. 24,680 ,Re'asued Aug. 1 1, 19.59Y

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The control voltages may be, for example, .pulses of different instantsof occurrence, or `oscillations ,of clii'terent frequencies. y

The dialling impulses lrepresenting .the `diierent digits dialled maybe`applied to set .different ones of the `selectors switching `devices inknown manner, and a further switch device may Abe arranged .to yprevent-the .output Yfrom at least the last selector switching device to beset, from reaching the output of the `coding device. r

The invention will now Abe described'by wayof example with 'reference tothe accompanying drawings., ,in which Figure 1 is a circuit diagram ofoneem'bodiment `of the invention, and

Figures 2(a), 2(b) 2,(c) ,and 3 are explanatory dagrams. v'

The fdetached contact system of references isused in Figure 1, thissystem being as described on page 9 of British Standard 530:1948Graphical y Symbols for 'Telecommunications published by the 'BritishvStandards Institution. In this system, vsymbols for parts ofcomponents, `for example relay .coils and contacts, Yare not placedtogether, -but are placed .in positions in the diagram relating to theirfunctional applications. A relay isgiven a reference in the form of afraction .in .which'the Anumerator `is a letter and is the relayreference and the denominay tor is a number indicating the number ofsets .of contactson the relay. For example a relay 'winding may have thereference X/3 indicating that the relay X has three contacts. Thesewould be reference X1, X2', and 1X3.

Referring to Figure 1, a dial DL1of anautomatic telephone `set (notshown) is connectedin series with a relay coil A and albattery BATl.Thusoperation of the dial DL causes a series of pulses o'f .current toow'throngh the relay coil A at ,the standard frequency of "1"() 'P`.P;S.jIt will be assumed `that the bnumber -dialled has four digits, say 12,3, 4 respectively.

The lpulses of current .in `the relay coil AV cause operation ofthecontacts A1 at `the same rate. These contacts are connected to the.wiper of-a bank Z1 of a unis'e'lector Z, and the wiper of the bank Z1is normally onits liir'st contact.

This first contact is connected 'through the winding of a seconduniselector M and a 'battery BAT2 to earth. Thus successive operationsof the contacts A1.causeslthe wipers of the uniselector M to be steppedaround their bank contacts. The uniselectors and stepping action thereofmay be as .described in chapter 3 of Telephonyg vol. II, by I. Atkinson,published by Sir Isaac Pitman & Sons Ltd.

'The bank M1 of the uniselec'tor ,M has elevenfbank contacts, 'the iirstof whichis a home contact. The remaining ten bank contacts .o'f 'M1 areconnected to ten terminals MB1 to `MP9 `and MP0 respectively. AThus invthe Vpresent example in which the 'first .digit is l ,the wiper of `thebank M1 is connected `to the v,terminal MB1.

A slow acting relay `B has one terminal of its operating coil connectedto the contacts A1 Xand. the other through a battery BATa to earth. The,relay is arranged to hold between adjacent impulsesin each digitdialledand hence becomes operated and released once 'for each digit `dialled. I

Thecontacts B1 o'f the relay B ,completen .circuit from earth through vthe winding of the uniselector .Z Vand .a Ybattery BAT., `back `toearth. Thus .the .wipers .of -the uniselector Z makes one ,forwardstep-after each rdigitris dialled. Thus when .-the;second.digit (2inthis-example) is dialled'the wiper of :the bank ais onits second bankcontact. This is connected .through rthe.operating-rvinding ofaiuniselectoriC and thence throu'ghabatt'ery BATS to earth. 1

The bank -'C1 of ythe 4uniselector 'C Ihas ueleven contacts of which thefirst is an isolated home contact. Thev remaining ten bank contacts areconnected to terminals CP1 to CP9 and CP1, respectively. In thisexample, therefore, the wiper of Ithe bank C1 becomes connected to theterminal CP2.

The relay B steps the wiper of the uniselector bank Z1 on to its thirdcontact before the third digit is dialled. The third contact of Z1 isconnected through the operating winding of a uniselector D and thencethrough a battery BAT, to earth.

'I'he bank D1 of the uniselector D has eleven bank contacts of which thelirst is an isolated home contact. The remaining ten bank contacts areconnected to ten terminals DP1 to DPs and DPO respectively. Thus in thisexample, the wiper of the bank D1 becomes connected to the terminal DP3.

At the end of the third digit the relay B steps the wiper of theuniselector Z on to its fourth contact. The fourth contact is connectedto the operating winding of a uniselector U and thence through a batteryBAT, to earth.

The bank U1 of the uniselector U has eleven bank contacts of which thefirst is in isolated home contact. The remaining ten bank contacts areconnected to ten terminals UP1 to UPg and UPO respectively. Thus in thisexample the wiper of the bank U1 becomes connected to the terminal UP4.

'Ihe 40 terminals UP1 through to MP0 are connected by suitableconnectors (not shown) to the 40 output terminals of like referencerespectively of a main pulse generator MPG. This pulse generator isarranged in any suitable manner to generate a recurring sequence of 40pulses which appear at the 40 `terminals MP0 to UPS respectively. Thepulse generator may be as described in the specification of saidcopending U.S. patent application, Serial No. 247,072. The generatedpulses will be referred to by the letters M, C, D and U followed by asubscript corresponding to the subscripts in the references to theterminals at which the pulses appear. Thus in the present example pulsesM1, C2, D3 and U4 appear at the wipers of the four uniselector banks M1,C1, D1 and U1 respectively. This set of pulses is regularly recurring asindicated in Figure 2(a).

The pulses of each set are combined through four rectiers W1 to W4respectively and applied through a resistor R and relay contacts Q2 toan output terminal T.

An auxiliary pulse generator APG is connected through a rectifier W tothe end of the resistor R remote from the rectiers W1 to W4. This pulsegenerator is arranged to generate relatively broad pulses of a widthequal to that of a complete sequence of M, C, D and U pulses, and at arecurrence frequency equal to one fth of that of the sets of M, C, D andU pulses. Thus the waveformof the pulses provided by the auxiliary pulsegenerator is as shown at GP in Figure 2(b).

In the absence of pulses from the auxiliary generator APG the rectifierW5 is conducting and hence the sets of pulses from the uniselector banksM1, C1, D1 and U1 are dropped across R. When a pulses appears at theoutput of the pulse generator APG, however, the rectifier W5 becomesnon-conducting and permits pulses to pass from the uniselector banks tothe contacts Q2. Thus in the present example only every fifth set of M1,C2, D3 aud U4 pulses are passed to the contacts Q2.

Referring again to the uniselector bank Z1, after the last digit hasbeen dialled the relay B steps the wiper of Z1 on to its fifth contactand hence causes energisation of a relay coil Q from a battery BATB.Thus when, and not until, the wipers of all four uniselector banks M1,C1, D1 and U1 have been set in accordance with the number dialled, therelay contacts Q2 close and the sets of M1, C11, D3 and U1 pulses gatedby the auxiliary generator APG appear at the output terminal OT.

l Thecontacts Q1 holdthe relay Q through a switch 4 S1 which is closedbefore the apparatus is put into use. The switch S1 may, of course,conveniently be contacts of a further relay (not shown).

The uniselector banks M2, C2, D2 and U2 and Z2 are homing banks and mayoperate as described on pages 259 and 260 of Telephony, volume II, byAtkinson. Thus in order to switch off the apparatus switches S2 to S6which may also conveniently be contacts of a relay (not shown) areclosed to cause all uniselectors to home, and S1 is opened to deenergisethe relay Q and hence to open the contacts Q2.

In a second embodiment the output of the auxiliary pulse generator APGis of different form, the resistor R is removed and the rectifier W5reversed. The pulse generator APG is arranged to generate pulses whichoccur after the last U pulse in each set and before the M pulse in thenext succeeding set.

For example referring to Figure 3 this shows a set of M1, C2, D3 and U4pulses on a larger scale than in Figure 2. After the U4 pulse and beforethe next succeeding M1 pulses two further pulses d5 and u3 are added.

We claim:

[1. Coding apparatus for automatic exchanges, comprising a main inputterminal to receive dialling impulses, a plurality of selector switchingdevices each having a plurality of input terminals and an outputterminal, control apparatus to actuate said selector switching devicesin response to dialling impulses, means to apply dialling impulses fromsaid main input terminal to said control apparatus to select differentones of the said input terminals of said selector switching devices forconnection to said output terminals thereof respectively, a source ofvoltages of dilerent characteristics, means to apply said voltages tothe input terminals of said selector switching devices, dilferentvoltages being applied to different ones of the last said terminals, acombining circuit connecting the output terminals of said selectorswitching devices to provide a combined output from said selectorswitching devices a source of signalling voltage, a further combiningcircuit, a main output terminal, means connecting said further combiningcircuit between the first said combining circuit and said main outputterminal, and means to apply signal Voltage from the last said source tosaid further combining circuit to produce at said main output terminal asignal having characteristics related to said dialling impulses and to asignal from the last said source] [2. Coding apparatus according toclaim 1, wherein said further combining circuit comprises a gate device`through which said combined output from said selector switching devicesis applied to said main output terminal and said signal voltage from thelast said source is applied to open and close said gate device wherebythe voltage at said main output terminal is in the form of a successionof groups of voltages characteristic of said dialling impulses and whoseinstants of occurrence are characteristic of said signal voltage] 3.`Coding apparatus for automatic exchanges, com,- prising a main inputterminal to receive dialling impulses, a plurality of selector switchingdevices each having a plurality of input terminals and an outputterminal, control apparatus to actuate said selector switching devicesin response to dialling impulses, means to apply dialling impulses fromsaid main input terminal to said control apparatus to select differentones of the said input terminals of said selector switching devices forconnection to said output terminals thereof respectively, means togenerate a plurality of interlaced recurring pulses, means to applydifferent ones of said recurring pulses to diiferent ones of the inputterminals of said selector switching devices, a combining circuitconnected to the output terminals of said selector switching devices tocombine the outputs of said selector switching devices into a recurringgroup of pulses characteristic of said dialling impulses, a main outputterminal, ,a gate device, means connecting said gate device between saidcombining circuit and said main output terminal, a source of signallingpulses, and means to connect said source of signalling pulses to saidgate device to open and close said gate device, whereby the voltageappearing at said main output terminal is in the form of a group ofpulses characteristic of said dialling impulses and recurring atinstants determined by the signalling pulses applied to said gate devicefrom said source of signalling pulses.

4. Coding apparatus for automatic exchanges, comprising a main inputterminal to receive dialling impulses, a plurality of selector switchingdevices each having a plurality of input terminals and an outputterminal, control apparatus to actuate said selector switching devicesin response to dialling impulses, means to apply dialling impulses fromsaid main input terminal to said control apparatus to select dierentones of the said input terminals of said selector switching devices forconnection to said output terminals thereof respectively, means togenerate a plurality of interlaced recurring pulses, means to applydilerent ones of said recurring pulses to diierent ones of the inputterminals of said selector switching devices, a combining circuitconnected to the output terminals of said selector switching devices tocombine the outputs of said selector switching devices into a recurringgroup of pulses characteristic of said dialling impulses, a main outputterminal, a further combining circuit, means connecting said furthercombining circuit between the rst said combining circuit and said mainoutput terminal, a source of signalling pulses, and means to applysignalling pulses from the last said source to said further combiningcircuit for combination with said recurring group.

5. Coding apparatus for automatic exchanges, comprising a main inputterminal to receive dialling impulses, a plurality of selector switchingdevices each having a plurality of input terminals and an outputterminal, control apparatus to actuate said selector switching devicesin response to dialling impulses, means to apply dialling impulses fromsaid main input terminal to said control apparatus to select differentones of the said input terminals of said selector switching devices forconnection to said output terminals thereof respectively, a source ofvoltages of dlerent characteristics, means to apply said voltages to theinput terminals of said selector switching devices, different voltagesbeing applied to different ones of the last said terminals, a combiningcircuit connecting the output terminals of said selector switchingdevices to provide a combined output from said selector switchingdevices, a source of signalling voltage, means for cornbining a signalvoltage from the last named source with said combined output, a mainoutput terminal and means applying the signal voltage combined with thecombined output to said main output terminal whereby to produce at saidmain output terminal a signal having characteristics related to saiddialling impulses and to a signal from the last named source.

6. Coding apparatus for automatic exchanges, comprising a main inputterminal to receive dialling impulses, a plurality of selector switchingdevices each having a plurality of input terminals and an outputterminal, control apparatus to actuate said selector switching devicesin response to dialling impulses, means to apply dialling impulses fromsaid main input terminal to said control apparatus to select dierentones of the said input terminals of said selector switching devices' forconnection to said output terminals thereoyc respectively, a source ofvoltages of dierent characteristics, means to apply said voltages to theinput terminals of said selector switching device, derent voltages beingapplied to dierent ones of the last said terminals, a combining circuitconnecting the output terminals of said selector switching devices toprovide a combined output from said selector switching devices, a sourceof signalling voltage, a further combining circuit, a main outputterminal, means connecting said further combining circuit between thefirst said combining circuit and said main output terminal, and means toapply signal voltage from the last said source to said further combiningcircuit to produce at said main output terminal a signal havingcharacteristics related to said dialling impulses and to a signal fromthe last said source, said further combining circuit comprising a gatedevice through which said combined output from said selector switchingdevices is applied to said main output terminal, said signal voltagefrom the last said source being applied to open and close said gatedevice whereby the voltage at said main output terminal is in the formof a succession of groups of voltages characteristic of said diallingimpulses and whose instants of occurrence are character-y istic of saidsignal voltage.

References Cited in the tile of this patent or the original patentUNITED STATES PATENTS 2,379,715 Hubbard `luly 3, 1945 2,457,149 HerbstDec. 28, 1948 2,563,589 Den Hertog Aug. 7, 1951 2,570,274 y Ransom Oct.9, 1951 2,688,662 Den Hertog et al Sept. 7, 1954

